Poly(meth)acrylic photochromic coating

Abstract

Described are articles having a photochromic poly(meth)acrylic coating The coatings exhibit a Fischer microhardness of from 50 to 150 Newtons per mm 2 and improved photochromic performance properties, i.e., the formation of darker activated colors and faster rates of photochromic activation and fade when irradiated with ultraviolet light.

We claim:  
     
       1. An article comprising, in combination, a substrate and a photochromic poly(meth)acrylic coating on at least one surface of said substrate, said coating comprising a polymerizate of: 
       (a) at least two difunctional (meth)acrylate monomers selected from:  
       (i) a first monomer, represented by the following general formula:                    
       wherein each R 1  is hydrogen or methyl, each R 2  is hydrogen or C 1 -C 2  alkyl, m and n are each a positive number, the sum of m and n being greater than 3 but less than 15, and A is a divalent linking group selected from the group consisting of straight or branched chain alkylene, phenylene, C 1 -C 9  alkyl substituted phenylene, and a group represented by the following graphic formula:                    
       wherein, each R 3  is C 1 -C 4  alkyl, chlorine or bromine, p and q are each an integer from 0 to 4,                    
       represents a divalent benzene group or a divalent cyclohexane group and X is O, S, —S(O 2 )—, —C(O)—, —CH 2 —, —CH═CH—, —C(CH 3 ) 2 —, —C(CH 3 )(C 6 H 5 )— or                    
       is the divalent benzene group, and X is O, S, —CH 2 —, or —C(CH 3 ) 2 — when                    
       is the divalent cyclohexane group; and 
       (ii) a second monomer represented by the following general formula:                    
       wherein each R 1  is hydrogen or methyl, x, y and z are each a number between 0 and less than 15 and the sum of x, y and z is greater than 3 and less than 15; said monomers being in a weight ratio of (i):(ii) of from greater than 10:90 to less than 90:10; 
       (b) a photochromic amount, of a photochromic component; and  
       (c) from 0 to 10 weight percent, based on the total weight of monomers, of polymerization initiator selected from thermal initiators, photoinitiators or mixtures of such initiators, said coating being free of chain transfer agents and said components (a), (b) and (c) being used in such proportions to produce a photochromic poly(meth)acrylic coating having a Fischer microhardness of between 50 and 150 Newtons per mm 2 , a ΔOD at 30 seconds of at least 0.15 and at 15 minutes of at least 0.50, and a bleach rate of not more than 200 seconds—all as measured at 22° C. (72° F.).  
     
     
       2. The article of  claim 1  wherein: 
       (a) for said first monomer, each R 1  is methyl, each R 2  is hydrogen, the divalent linking group A is represented by the following graphic formula:                    
       is the divalent benzene group, p and q are each 0 and X is —C(CH 3 ) 2 —; and 
       (b) for said second monomer, each R 1  is methyl, x is a number greater than 3 and less than 15, and y and z are each 0; said monomers being in a weight ratio of (i):(ii) of from 20:80 to 80:20.  
     
     
       3. The article of  claim 1  wherein the monomers (i):(ii) are in a weight ratio of (i):(ii) of from 40:60 to 85:15. 
     
     
       4. The article of  claim 1  wherein said polymerization initiator is a thermal polymerization initiator selected from peroxymonocarbonate esters, peroxydicarbonate esters, diacylperoxides, peroxyesters, methylethylketone peroxide, acetylcyclohexane sulfonyl peroxide, azobis(isobutyronitrile), 2,2′-azobis(2,4-dimethylpentanenitrile), 1,1′-azobiscyclohexanecarbonitrile, azobis(2,4-dimethylvaleronitrile) or mixtures of such initiators. 
     
     
       5. The article of  claim 4  wherein said thermal polymerization initiator is 2,2′-azobis(2,4-dimethylpentanenitrile), 1,1′-azobiscyclohexanecarbonitrile or mixtures thereof. 
     
     
       6. The article of  claim 1  wherein said polymerization initiator is a photoinitiator selected from acetophenones, α-aminoalkylphenones, benzoin ethers, benzoyl oximes, acylphosphine oxides, bisacylphosphine oxides or mixtures of such initiators. 
     
     
       7. The article of  claim 1  wherein said polymerization initiator is a photoinitiator selected from benzophenone, Michler's ketone, thioxanthone, anthraquinone, camphorquinone, fluorone, ketocoumarin or mixtures of such initiators. 
     
     
       8. The article of  claim 7  wherein said polymerization initiator further comprises a hydrogen donor material. 
     
     
       9. The article of  claim 7  wherein said polymerization initiator further comprises a cationic photoinitiator. 
     
     
       10. The article of  claim 1  wherein the photochromic component comprises: 
       (a) at least one photochromic compound having a visible lambda max of from 400 nanometers to 525 nanometers; and  
       (b) at least one photochromic compound having a visible lambda max of from greater than 525 nanometers to 700 nanometers.  
     
     
       11. The article of  claim 10  wherein the photochromic compounds are benzopyrans, naphthopyrans, phenanthropyrans, quinopyrans, indeno-fused naphthopyrans, benzoxazines, naphthoxazines, spiro(indoline)pyridobenzoxazines, metal-dithizonates, fulgides, fulgimides or mixtures thereof. 
     
     
       12. The article of  claim 1  wherein the cured coating has a thickness of from 1 to 200 microns. 
     
     
       13. The article of  claim 12  wherein the thickness is from 10 to 100 microns. 
     
     
       14. The article of  claim 1  wherein said substrate is paper, glass, ceramic, wood, masonry, textile, metal or polymeric organic material. 
     
     
       15. The article of  claim 14  wherein the polymeric organic material is a solid transparent polymer selected from the group consisting of poly(methyl methacrylate), poly(ethylene glycol bismethacrylate), poly(ethoxylated bisphenol A dimethacrylate), thermoplastic polycarbonate, poly(vinyl acetate), polyvinylbutyral, polyurethane, polythiourethanes, and polymers of members of the group consisting of polymerizates of diethylene glycol bis(allyl carbonate) monomers, diethylene glycol dimethacrylate monomers, ethoxylated phenol methacrylate monomers, diisopropenyl benzene monomers, ethoxylated trimethylol propane triacrylate monomers and mixtures thereof. 
     
     
       16. The article of  claim 15  wherein said substrate is an optical element. 
     
     
       17. The article of  claim 16  wherein said optical element is a lens. 
     
     
       18. The article of  claim 17  wherein the refractive index of said lens is from 1.48 to 2.00. 
     
     
       19. The article of  claim 1  further comprising a primer interposed between the substrate and photochromic poly(meth)acrylic coating. 
     
     
       20. The article of  claim 19  further comprising a protective coating applied to the surface of the photochromic poly(meth)acrylic coating. 
     
     
       21. An article comprising, in combination, an optical element having a primer on at least one surface of said element, a photochromic poly(meth)acrylic coating on said primer and a protective coating on the photochromic poly(meth)acrylic coating, said photochromic poly(meth)acrylic coating comprising a polymerizate of: 
       (a) at least two difunctional (meth)acrylate monomers selected from:  
       (i) a first monomer, represented by the following general formula:                    
       wherein each R 1  is hydrogen or methyl, each R 2  is hydrogen or C 1 -C 2  alkyl, m and n are each a positive number, the sum of m and n being greater than 3 but less than 15, and A is a divalent linking group selected from the group consisting of straight or branched chain alkylene, phenylene, C 1 -C 9  alkyl substituted phenylene, and a group represented by the following graphic formula:                    
       wherein, each R 3  is C 1 -C 4  alkyl, chlorine or bromine, p and q are each an integer from 0 to 4,                    
       represents a divalent benzene group or a divalent cyclohexane group and X is O, S, —S(O 2 )—, —C(O)—, —CH 2 —, —CH═CH—, —C(CH 3 ) 2 —, —C(CH 3 )(C 6 H 5 )— or                    
       is the divalent benzene group, and X is O, S, —CH 2 —, or —C(CH 3 ) 2 — when                    
       is the divalent cyclohexane group; and 
       (ii) a second monomer represented by the following general formula:                    
       wherein each R 1  is hydrogen or methyl, x, y and z are each a number between 0 and less than 15 and the sum of x, y and z is greater than 3 and less than 15; said monomers being in a weight ratio of (i) to (ii) of from greater than 10:90 to less than 90:10; 
       (b) a photochromic amount of a photochromic component; and  
       (c) from 0 to 10 weight percent, based on the total weight of monomers, of polymerization initiator selected from thermal initiators, photoinitiators or mixtures of such initiators, said coating being free of chain transfer agents and said components (a), (b) and (c) being used in such proportions to produce a photochromic poly(meth)acrylic coating having a Fischer microhardness of between 50 and 150 Newtons per mm 2 , a ΔOD at 30 seconds of at least 0.15 and at 15 minutes of at least 0.50, and a bleach rate of not more than 200 seconds—all as measured at 22° C. (72° F.).  
     
     
       22. The article of  claim 21  wherein the monomers are in a weight ratio of (i):(ii) of from 30:70 to 70:30.